Cambodian, also known as Khmer, is the official language for the nation of Cambodia. Wikipedia gives the following information about Khmer: “With approximately 16 million speakers, it is the 2nd most widely-spoken Austroasiatic language (only Vietnamese has more speakers currently). Khmer has been considerably influenced by languages such as Sanskrit and Pali, especially in the royal and religious registers, through the vehicles of Hinduism and Buddhism. It is also the earliest recorded and earliest written language of the Mon–Khmer family, predating Mon and by a significant margin Vietnamese. The Khmer language has influenced, and also been influenced by Thai, Lao, Vietnamese, Chinese and Cham, all of which, due to geographical proximity and long-term cultural contact, form a sprachbund (language region—sic) in peninsular Southeast Asia.”
According to Wikipedia (summary), dialects of Khmer (Cambodian) include:
Northern Khmer (called Khmer Surin): The dialects spoken by those in the border provinces of present-day Northeast Thailand. Economical isolation has created a distinct accent influenced by surrounding languages like Lao and Thai, lexical and phonemic differences, and other unique language differences. Some expert linguists consider Northern Khmer a separate but similar language instead of a dialect.
Western Khmer (also called Cardamom Khmer or Chanthaburi Khmer): Spoken by a tiny number of people, this dialect is unique but for the most part has all but disappeared within other Khmer dialects.
Phnom Penh Khmer (spoken in the capitol and surrounding areas): This dialect is characterized by merging or complete elision of syllables, considered by speakers from other regions to be a “relaxed” pronunciation.
Southern Khmer (Khmer Krom): Spoken by the indigenous Khmer population of the Mekong Delta. Khmers are persecuted by the Vietnamese government for using their native language. Consequently very little research has been published regarding this dialect.